In a high-voltage inverter device according to the related art which controls the driving of, for example, a motor, a pair of an insulated gate bipolar transistor (IGBT) and a p-intrinsic-n (PIN) diode, which are silicon (Si) elements and connected in inverse parallel, is provided in each of the upper and lower arms. The upper and lower IGBTs are alternately switched to generate an AC current as the output of the inverter device, thereby controlling the motor. During this operation, when the IGBT is turned on, a driving current flows through the IGBT. When the IGBT is turned off, a return current from the motor flows through the diode. In this case, conduction loss and switching loss occur in each of the IGBT and the diode, which causes the power conversion loss of the inverter device. The loss of the Si device at present is substantially equal to a theoretical value which is determined from the physical property value of Si and it is difficult to further reduce the loss.
SiC has a wider forbidden band width than silicon and the breakdown field of SiC is about one order of magnitude greater than that of silicon. Therefore, SiC is expected to be widely used for the next-generation power device. In particular, in a SiC vertical power metal oxide semiconductor field effect transistor (MOSFET), on-resistance is expected to be significantly reduced in a wide breakdown voltage range of several hundreds to several kilovolts, as compared to the silicon element according to the related art. In addition, since the MOSFET is a unipolar element unlike the IGBT, it can perform switching at a high speed. A PN diode which is called a body diode is provided in the structure of the vertical power MOSFET. Therefore, a return current can flow through the body diode, without using an inverse parallel diode. As a result, it is possible to form an inverter device using only the vertical power MOSFET and to reduce the number of components or the size of the inverter device, as compared to the Si inverter according to the related art.
However, in a SiC PN diode, when there is a stacking fault in the element, the stacking fault is grown by the recombination of electrons and holes during the turn-on of the diode. As a result, the lifetime of a hole which is conducted is reduced and the forward on-voltage of the PN diode increases (conduction deterioration occurs).
In contrast, in Patent Document 1, a region into which a recombination center is introduced is provided on a current path immediately after a semiconductor device is turned on. Therefore, a chance of the recombination of electrons and holes due to the stacking fault is reduced and the growth of the stacking fault and conduction deterioration are prevented.